\begin{tikzpicture}[>=Stealth,
    every node/.style={fill=white, inner sep=1pt},
]
    \draw [ground] (0, 0) -- (1, 0) -- (2, -1) -- (2.8, -1) -- (3.8, 0) -- (4.8, 0);
    \draw [<->] (1, 0.3) to [xianduan={below=0.3cm}] node {$a$} (3.8, 0.3);
    \draw [<->] (2, -1.5) to [xianduan={above=0.5cm}] node {$b$} (2.8, -1.5);
    \draw (2, -1) -- (0, -1);
    \draw [<->] (0.3, 0) to [xianduan] node {$h$} (0.3, -1);
\end{tikzpicture}
